ST AN1296 Application note

June 2010 Doc ID 8159 Rev 3 1/8

AN1296

Application note

Ring wave tests with ACS108 driving valves and pumps

Introduction

In this application note, test results obtained using ACS108 AC switch devices are

presented in order to analyze their behavior when subjected to standard ring wave surges.

The behavior of these devices subjected to a 1.2/50 µs impulse wave is specified in the

datasheets.

The test procedure is described in the UL858A standard. The only difference with the tests

below is that the normalized waveform is applied directly to the semiconductor and the load

(refer to Figure 1).

No coupling network is used to apply the surges while the system is connected to the mains

terminals. The only stress is due to the breakover turn-on current. The current conduction

during half mains cycle is not an issue.

The ACSs are not triggered by their gate - they turn on by over voltage when the generator

voltage exceeds their clamping level. The surge is then applied across the load and the load

current flows through the ACS™ which is in the on state.

Figure 1. Test diagram

All the following oscillograms have been produced using the equipment listed below:

● Tektronix TDS754A scope

● Tektronix voltage P6013A probe (1/1000 ratio)

● Eurocraft pulse current transformer (1 V /10 A ratio)Tektronix TCP202 current probe

TM: ACS is a trademark of STMicroelectronics

OUT

G

COM

Integrated

driver

Over voltage

protection

(Trisil™-like)

AC power

switch

Ringwave

generator

RG = 150W

IOUT

Load

TM: Trisil is a trademark of STMicroelectronics

www.st.com

Results AN1296

2/8 Doc ID 8159 Rev 3

1 Results

Three kinds of loads have been used during the tests.

● Val ve

● Pump

● Resistor rated at 5 W, 150 Ω

1.1 Valve

The valves used were rated for 120 V, 50 mA, 60 Hz operation. Two different types of

behavior can appear during ring wave test when using such valves.

● The valve insulation is sufficient: when the ACS turns on, the current is limited by the

load inductor. Only a capacitive current (approximately 250 mA peak, see Figure 2) can

be seen during the rise of voltage across the switch. Such a turn on is not stressful for

the device.

Figure 2. 3 kV surge with a well insulated valve

V

out

(200 V/div)

I

out

(0.5 A/div)

AN1296 Results

Doc ID 8159 Rev 3 3/8

● The valve insulation is not sufficient: in this case, the valve oil winding insulation breaks

down when the switch turns on, i.e. when the whole surge voltage is applied across the

valve. The load then behaves like a short-circuit. The ACS current is no longer limited

and could reach up to 120 A (refer to Figure 3). The conduction losses could then be so

high that the die silicon could melt or its bonding wires could fuse and cause the

destruction of the device package. In practice, as the test is done with the complete

equipment including clamping devices or filters, this behavior does not occur.

Figure 3. 3 kV surge with an insufficiently insulated valve

V

out

(200 V/div)

I

out

(50 A/div)